Merge pull request #71 from krm35/fix/shortestPaths

Fix/shortest paths

Author: curran

src/index.ts

@@ -178,7 +178,7 @@ export function Graph(serialized?: Serialized) {
   function depthFirstSearch(
     sourceNodes?: NodeId[],
     includeSourceNodes: boolean = true,
-    errorOnCycle: boolean = false
+    errorOnCycle: boolean = false,
   ) {
     if (!sourceNodes) {
       sourceNodes = nodes();
@@ -284,7 +284,7 @@ export function Graph(serialized?: Serialized) {
   // Cormen et al. "Introduction to Algorithms" 3rd Ed. p. 613
   function topologicalSort(
     sourceNodes?: NodeId[],
-    includeSourceNodes: boolean = true
+    includeSourceNodes: boolean = true,
   ) {
     return depthFirstSearch(sourceNodes, includeSourceNodes, true).reverse();
   }
@@ -394,12 +394,22 @@ export function Graph(serialized?: Serialized) {
   function shortestPaths(source: NodeId, destination: NodeId) {
     let path = shortestPath(source, destination);
     const paths = [path],
-      removedEdges = [],
+      removedEdges: { u: NodeId; v: NodeId; weight: EdgeWeight }[] = [],
       weight = path.weight;
     while (weight) {
-      removeEdge(path[0], path[1]);
-      removeEdge(path[1], path[0]);
-      removedEdges.push([path[0], path[1]]);
+      const u = path[0];
+      const v = path[1];
+
+      if (hasEdge(u, v)) {
+        removedEdges.push({ u, v, weight: getEdgeWeight(u, v) });
+        removeEdge(u, v);
+      }
+
+      if (hasEdge(v, u)) {
+        removedEdges.push({ u: v, v: u, weight: getEdgeWeight(v, u) });
+        removeEdge(v, u);
+      }
+
       try {
         path = shortestPath(source, destination);
         if (!path.weight || weight < path.weight) break;
@@ -408,10 +418,7 @@ export function Graph(serialized?: Serialized) {
         break;
       }
     }
-    for (const [u, v] of removedEdges) {
-      addEdge(u, v);
-      addEdge(v, u);
-    }
+    for (const { u, v, weight } of removedEdges) addEdge(u, v, weight);
     return paths;
   }
 

test.js

@@ -378,7 +378,7 @@ describe("Graph", function () {
       var graph = Graph().addEdge("a", "b").addEdge("b", "c");
       assert.deepEqual(
         graph.shortestPath("a", "c"),
-        withWeight(["a", "b", "c"], 2)
+        withWeight(["a", "b", "c"], 2),
       );
     });
 
@@ -396,11 +396,11 @@ describe("Graph", function () {
 
       assert.deepEqual(
         graph.shortestPath("s", "z"),
-        withWeight(["s", "y", "z"], 5 + 2)
+        withWeight(["s", "y", "z"], 5 + 2),
       );
       assert.deepEqual(
         graph.shortestPath("s", "x"),
-        withWeight(["s", "y", "t", "x"], 5 + 3 + 1)
+        withWeight(["s", "y", "t", "x"], 5 + 3 + 1),
       );
     });
 
@@ -423,11 +423,11 @@ describe("Graph", function () {
       var graph = Graph().addEdge("a", "b").addEdge("b", "c").addEdge("d", "e");
       assert.deepEqual(
         graph.shortestPath("a", "c"),
-        withWeight(["a", "b", "c"], 2)
+        withWeight(["a", "b", "c"], 2),
       );
     });
 
-    it("Should compute shortest paths on six edges.", function () {
+    it("Should compute shortest paths.", function () {
       var graph = Graph()
         .addEdge("a", "b")
         .addEdge("b", "c")
@@ -436,14 +436,21 @@ describe("Graph", function () {
         .addEdge("a", "e")
         .addEdge("e", "f")
         .addEdge("f", "c");
+      const serializedGraph = graph.serialize();
       assert.deepEqual(graph.shortestPaths("a", "c"), [
         withWeight(["a", "b", "c"], 2),
         withWeight(["a", "d", "c"], 2),
       ]);
-      // need to check nodes are still present because we remove them to get all shortest paths
-      const nodes = ["a", "b", "c", "d", "e", "f"];
-      assert.equal(graph.nodes().length, nodes.length);
-      nodes.forEach((node) => assert(contains(graph.nodes(), node)));
+      // check graph has not changed
+      const postSerializedGraph = graph.serialize();
+      assert.equal(
+        postSerializedGraph.links.length,
+        serializedGraph.links.length,
+      );
+      assert.equal(
+        postSerializedGraph.nodes.length,
+        serializedGraph.nodes.length,
+      );
     });
   });
 
@@ -458,11 +465,7 @@ describe("Graph", function () {
 });
 
 function contains(arr, item) {
-  return (
-    arr.filter(function (d) {
-      return d === item;
-    }).length > 0
-  );
+  return arr.includes(item);
 }
 
 function comesBefore(arr, a, b) {